Hydraulic by-pass control



Nov. 4, ,1952

ID. GRANT E1-AL v HYDRAULIC BY-PAss CONTROL Filed Feb. e, 194e liar' IN VEN TORS Patented Nov. 4, 1952 UNITED STATES PATENT OFFICE Manhattan Bea'oli, Calif., assignors to Hughesf Tool Company; Houston, Tex., af corporation of Delaware.

Application .February 6, 1948, Serial' No. 6;7'48- (GL Gil-97:)

Our invention' relates generally to' hydraulic control systems and more particularly to. such systems having two separate and independent operating means with. provision' to disconnect,l in eiect, one. of," these means, shouldany' failure'o'c.- our therein.

With the, increasingly. Widespread use oi hydraulic` control'. and; operating systems;V it. fre.- quentl'y happens that4 provision3 must be made to insure the control or operation. of ai certain member even4k though the normal hydraulic system fails. Consequently, some attempts. to secure thedesired reliabilityoioperation rhave made use of two. separate and", independent. controllsys.- tems, one. ofA which normally. acts to produce the desired. control;v While. the. other` is an alternate system. which. acts only when` the rst system tails. However., suona. dualsystem arrangement the Vother system fail.

Oneof, the commonly used. actuating elements ofA a hydraulic.control'system isa double. acting piston mounted'A withina.. cylinder adapted' to` have fluid under pressure injected` at. either end. If

.iludlis forcedinto one.endoffthecylinder While simultaneously, being, released, atv the. other. end, the piston4 therein. will. be. movedV toward. the low pressure endL` of the.` cvlinden However, if. an attemptis made to, move` the `piston'. without simultaneously admitting 'uid toene end off the cyl.- inder and releasingit at' the other end'theyin compressibility` ofthe luidgresults in .thepist'ons being locked "in one. position. Iftvv-o separate and,independent,control-systems are used toopcrate asingl'edevice, itsometimes happensthat failure of. one offtlie systems-.Will result in the fluid therein being 'trappedor'locked so that the piston associated'. Withj that" system. i'sl effectively held against movementgeven" tliou'gl'i` the' other system' is functioning and attemptsjtb move. the member to which both'. pistons are. connected. We have' foundl that; these; objections. may be overcome by, using a shunti'iigjor.. lcv-passi valve connected loetvveen oppositeends` of the voperating cylinderso thatl'fluid at one endl of. the piston may be readily transferred to theL other enditliereof, so. that .the pistoniisfreelymov-able. In nor.- mal operatiointhe.byypassvalveis closed so that the piston and.' cylinder. voperate i'r'iithe. conventional fashion',` but when' a failureoccurs inlthe 21 controlsystem',l the lov-pass valve is opened' so thatthe other, independent system may operate in the normal manner;-

It is therefore amajor objectof our invention to.v provide a hydraulicsystem having great reliabilityof operation.

Another. object of our invention. is to provide such a. system which is operable even though one-halfof.' the complete system. has enti-rely failed.

Itis a-further object? of ourf invention; to provide. a hydraulic. control. system havingY means therein to insurethe'- free movement ofthe nonoperatingY elements. when. such a. failure occurs.

Still another object of our invention is to provide a pilot or.` control. valve.l to open ahy-pass of the type previously mentioned.

It. is.' astillf. tu'rther object of our` invention to provideA such a. valve: andi system which are light in. Weight and.Y si'inplein. operationso that the advantagesA ofthis system! m'aybehad in. applications Where'. space. an'd` weight are important factors.'-

Theseandeotlier objects andi advantages ofi our invention.vii-illbecome" apparent from theVV following descriptionA ofa preferred?v i'orinf thereof, and from the" difa'llling"1illustrat'ifig1 thatifo'rmini which Fig'. lis-a; diagra'rnshowingtheconplete layout and-connectionsio'f our system; andi Fig'. 2ii`sf altrenlargedvfievvfci?A a'p'ortlon of the klv-pass-I co'nt'rolvalve usefdi therein.

Referrihg'vnoW-'to i tliedi'awing f and? particularly t'o Fiige' 1L tlfiereof,V thenumerali lllindicates gen'- erallyy a? double-acting pistonY andV cylinder of al conventional'l type' having" a# piston H` within a5- housi'ngf or cylinder IZ The ends o'fffthecyli'nderY l2 are` closed? by caps. |3 through which af piston rod I if extends` tb connect-to the devicef tol b'en controlled" (not sho'vvn'. Suitable tubing i'a'gr isv iiuid connectedto oneV end of the Cylinder" |2`whil`e'sirni1ar tubing' Iii is likew'iseconnectedf-tothe'other endthereof, both of these' tubes extending" tofs;A Suitable hydraulic selectorjvalvet Il;7 ASelectorl valves of thisy type are*vvellk-novvnin-the'art and are so'designed'that theyI may 'l benv connected'lthrougli* suitable hydraulic` tubing" 2i)E to af sour'ceof"A hydraulic pressure sucha's a*pum`p22 Similarly; provision is made to connectthe valve'll through .tubing 2I to a' resmaybeestablisliedtlierethroughV fromthe supply return line 2|. Fluid will thus be forced into a chamber 23 between the piston II and one end of the cylinder I2, while fluid will simultaneously be removed from a chamber 24 between the opposite side of the piston and the opposite end of the cylinder. This will cause the piston II to be moved toward the chamber 24, to the right in Fig. 1, thereby operating the equipment to which the piston rod I4 is connected. By reversing the operation of the valve I'I, the piston II may be moved in the opposite direction, while in intermediate positions of the valve, both of the tubes I5 and I6 are disconnected from the supply line 2S and the return line ZI and the piston does not move.

The system just described is the conventional hydraulic system used in operating many different devices, but wherethe utmost in reliability in operation is required, we have found it desirable to provide a duplicate system, identical to that just described, including a double acting piston IIa and cylinder Illa, a control valve Ila, and various connecting members adapted to provide a iiuid connection to pump 22a or other suitable pressure supply means. The controlling members of the valves I'I and I'Ia are mechanically linked together so that both are simultaneously operated to cause a simultaneous movement of the piston rods I4 and I4a. Both of these piston rods are connected to the member to be controlled, and the size of the hydraulic cylinders IB and Ia and their respective sources of fluid pressure are so correlated with the force required to move the controlled member that either cylinder acting alone may produce the required movement.

If a failure occurs in the hydraulic system receiving its pressure from pump 22 it is quite possible that fluid in cylinder I0 will be trapped, effectively locking piston Il. By connecting a valve between the chambers 23 and 24 of the cylinder I0, these difculties may be surmounted, since the opening of this valve will permit the direct flow of iiuid from one end of the cylinder, through the valve, to the opposite end of the cylinder. Under normal conditions, the valve will be closed so that conventional operation of the cylinder I0 will be had but when a failure occurs, the valve is opened. Consequently, any

valve which is connected between the chambers `1 23 and 24 must be quickly and positively operable, and preferably this valve should be operated automatically upon the failure of the corresponding pressure supply or connections thereto.

While many diierent types of valves in different kinds of control systems may be used, we have found that hydraulic controls and hydraulically operated valves form a very convenient method of solving the problem since no other power source is necessary for their operation.

The valve which we have developed for use as a by-pass valve is indicated generally by the numeral and includes a housing 3| having a poppet valve 32 therein normally urged by a spring 33 against a valve seat 34 formed in the housing. The opposite end of the housing 3l is provided with a rather small hydraulic cylinder 35 in which is mounted a piston 36 connected by a piston rod 31 to the valve 32. Under normal circumstances, the valve 32 will bear against the valve seat 34 by reason of the urging of spring 33, but by increasing the pressure within the cylinder 35, the piston 36 will be moved toward the spring to open the valve. The space within 'the housing 3l which contains the spring 33.

designated as chamber 40, is fluid connected by tubing 4I to chamber 23 of the hydraulic cylinder I0, and in a similar manner, the compartment between the valve seat 34 and the piston 36, chamber 42, is connected by tubing 43 to chamber 24 of the hydraulic cylinder I0. The space within the hydraulic cylinder 35, chamber 44, is connected by a uid connection 13a to a suitable source of pressure operable in a manner hereinafter described to control the by-pass valve 30. Thus, when the pressure within the chamber 44 is low, spring 33 will urge the valve 32 against the valve seat 34 and thereby prevent any transfer` of fluid between chambers 23 and 24 through the by-pass valve 30. However, when the pressure in chamber 44 of the latter is increased, piston 36 is moved to open the by-pass valve so that there may be a relatively free interchange of fluid between the chambers 23 and 24 of the hydraulic cylinder I0, and the piston I I may thus be freely moved throughout its entire length of travel.

To operate the by-pass valves 30 and 30a, we have developed a control valve connected between the pumps 22 and 22a so that a failure of one of these pumps will cause the pressure of the other to be transmitted to the chamber 44 and thereby open the by-pass valve of the system supplied by the inoperative pump. The control valves operate automatically, and their construction is such as to render them very reliable in operation.

In Fig. 1 of the drawing, we have illustrated the control valve a in cross-sectional View, with an enlarged view of a portion of this valve shown in Fig. 2. Like the other parts of the two separate and independent systems, the valves 50 and 50a are identical to each other and are similarly connected to corresponding parts.

Within a housing Sla having an axially extending bore 52a therethrough, we mount a compound piston member 53a having a piston 54a at one end thereof with a spaced piston 55a connected to the end piston 54a by a reduced portion 56a acting as a connecting rod. The pistons 54a and 55a thus move as a unit, and fluid connections Sa and Sla are mounted in opposite ends of the housing 5Ia to admit fluid under pressure into the axial bore 52a, to act upon the pistons 54a and 55a, respectively. A spring 62a extends from the fluid coupling Gla to the adjacent end of the piston 55a to urge the latter and the piston 54a toward the fluid connection 60a, while a rod 63a within the spring prevents undesirable ilexing or bending thereof.

By reference to Fig. 2, it will be seen that a chamber 64a is formed between the adjacent faces of the pistons 54a and 55a within the bore 52a. This chamber will move with the piston member 53a, and we provide a pair of uid connections adapted to be connected to this chamber when the piston member 53a is in its normal position, indicated in Fig. 1 and shown in full or solid outline in Fig. 2. As illustrated, one coupling 65a is uid connected to the bore 52a at a point immediately adjacent the inner surface of the piston 54a, while the other uid connection 66a is connected to the bore at a point between the connection of connector 65a and the adjacent face of piston 55a. Consequently, while there is normally a, uid connection between the connectors 65a and 66a, movement of the piston member 53a to the position shown in dotted outline in Fig. 2 will interrupt this connection and establish a connection between the connectors 50a and 65u. Normally, spring 62a urges,` the piston memser sa@ against tile'emiejctf sncjfbt me pressure ''diierent'ialiI Between opposite ds "6i thepiston member becomes `si'i'lrleieritlyr great, the latteryvill rbe "moyd yto" "the" al'te ate" position s'liyvn in'Fig. igt/ith the'endlofftlie roda'bearl ing' against the' fiuijdcongieti slate' limi-t the movement Vof'the piston member.

'Illa and "l lia Yto'tvlie pressure ord'scllflarge side 'di' pump 22a, Whilev connector' Gla isl cnetedl by tubing I=2a and 'M tothewbressure Oli discharge sidel of pump"2-2. vso thatthese two pr'ssiesare balanced against each other Within the bore 52a.

Connector 65a i's connected bytuloing "13a/to the connector 3Softh`e b yf-pass valvellli'while een nector 66a is connected-by. tubing Hr to the returnor intake connction'of! puiiip 22a.

The operation ofthe controlfvalye.,50a maylnow be understood. When the pressuressupplied-by the pumps 22Av and zza are substantially eul, the piston member 53a- Will havev the oliterface's of the pistons 54a, and rdsubjected to substantiallyl equal pressures, but the-'spring 63a, acting on the piston` 55d, will urge 5the" piston member t'ovzard` the iluid` connector 60a so that thefmemleerA is. in the. position shown in lig. 1. Under these conditions, fluid-f connectors' 65a and! 66a are uid Vconnected-1through` the` chamber 64a. so

thatr the intake or. return. cnnection of-pump 22a is 'connected throughA tubing- Ma, connector 166e,

chamber 64a, connector 65cand-vtuloing 13a l to chamber. 44. of. the by-passrvalve 311: vConsequently; the.. pressure Within chamher- M: is 10W,

andl spring 3.3- urg'es' the. valve.. 32 to closed: posi tionV so that. theY hydraulic cylinder. loperates in. the normal: manner. Bywsimilareconnections -i-,eriallyl exceed thatv at. connector- 61a, 'and the piston member 53a, Willl belmovedto theposition indicatedin dotted outline in Fig. 21. Whilethis necessitates overcomingl the urging` offspring 62a, the strength of the latter isselected` so that the pressure supplied-ley the pump 22d isl'adequate Ato do this.

Withv the piston member` 53a, in` the position shcwnin dotted outline, a.fluidiconnectionisestablished y between connector. 60a and: connector 65a, this pressure being.'substantially` equal to that supplied by thepumpfa. Co nsequentlyQy the pressure supplied by the.. pump. 22a is transmitted through tubing 13a to the chamber 44 o'ff the by-pass valve 30, niovingihe-piston 36` inthe latter vto open the valve, against-trie urging ofspring, to permitthe. freefiiow offhydraulic fluid between chambers 231fand ZL;

- 'Considering control-valve 511;- whentherpressure "supplied-py pump v2li is materially decreased;- the pressure at iiuid connector- 60 is materially. lower than that,atluid-connectorYB-l. AI-Icweyer, since the piston member 53 of= control Valve 5c is a1- rady'lfield iii its normal position byspring 6`2=, no additional movement of 'the piston member 53 occurs because of the iai-lure or pump 22, and tlis the ley-passl Valve 30a remains infits closed position.

`S`irethe connections for eachA system are similar'fit Will-'be appreciated that-should the system co'rinetedt pump 22a fail while the system conre'cltedu to punp 22 remains operating, control valvel Bll-"Will-fb'e' operated to open icy-pass valve 361e; so thatl hydraulic cylinder Mia is". released.y to move freely while cylinder lil performs the actual Work in' moving the member to be controlled.

I t"\yillthus vlceseen thatwe have provided a hydraul'ie control-system possessing greatreliability (3f-operation. While-theneed forsucha systein'isfsfomewhat limited, in certain applications suoli 'asftl'ie operation of?, the control boost sysy ofi-fan aircraft, reliability of' operation is of p nnary Aii'npo'rtance, and itis for just suchapplim tiensY that-'our system is designed. Prefer.'- thetli'ikness of thepiston lFalla is made grevter'than'the opening ofr the uid'connection from'theconriector 65a into the bore Maso-that there is "no possibility ofiuidLk passing directly fifemconnectr Stato connector 66a asthepiston moves frcmits norm'alrtoitsoperated position. In this manner; each. offthetwol control systems operates so 'thatV customary-- controlfand! operatin'g'i'r'emloersand designprocedures-maybe used.

'While ri't' "i`s"lziyicus 'that the control' and `operatin'gemembers may be varied to suitthe indfi-'v dual reqi'iirementsl of theA job, such changes will: be; apparent to thoseskilledv in the art! and need not'depart from the scopeof the` invention as 'hereiri definedf' Consequently, we-do notwish t5 loe restricted-to the particular form orarrangement ofparts herein 'described and shown, exceptas limited b y our claims.

l.V In combination: a hydraulic-cylinder.,alpiston Within said cylinder; rst and secondpressure supply meansj means-for selectivelycoupling sail first pressure supply meansl tothe ends of said cylinderior moving said piston in either direction Withinl saidv cylinder; a 'normally' closed tsr-passyalveM iiuid coupled between the opposite ends of said cylinder;l `and means coupledf between saidg-irst and secondpressure supplymeans andresponsive to',tlie'failure ofp/ said first pressuresupply means foropening said by-passyalve.

' 2'.- Af'hydra'liccontrl systemcomprisingaa hydraulic` cylinder; a piston positioned in said cylinder; firstandsecondhydraulicpressuresupply means;means-iiiuidcoupledbetween saidirst supply-means and opposite ends of said'. cylinder forf vselectivelyapplying pressure from said first supplyn means. tov opposite endsy of said;L piston to move said piston inA- either direction; i a normally closedlvby-passf Valve. iiuid; coupled between opposite-Y ends of` said cylinder.;` means; coupled* to said: Icy-pass..` valve. for opening said valve to 'equalize the pressuresat the ends-of y said piston;

piston for moving said piston within said cylinder; a normally closed by-pass valve fluid connected between opposite ends of said cylinder; piston means mechanically coupled to said bypass valve for selectively opening said valve; a source of auxiliary pressure; a normally closed valve fluid coupled between said auxiliary pressure source and said piston means; and pressure responsive means coupled between said pressure supply means and said auxiliary pressure source and operable upon failure of said pressure supply means to open the last-named valve, whereby said auxiliary pressure source actuates said piston means to open said by-pass valve and permit free iiuid transfer between the ends of said cylinder.

4. A hydraulic control system including: a hydraulic cylinder; a piston positioned in said cylinder; pressure supply means; control means for selectively directing the pressure from said pressure supply means to opposite ends of said piston for moving said piston within said cylinder; a by.pass valve fluid coupled between opposite ends of said cylinder, said valve having a movable valve element positioned therein, a spring coupled to said valve element urging said element to normally close said valve, and a piston mechanically coupled to said valve element for selectively moving said valve element against the urging of said spring to open said by-pass valve; an auxiliary pressure source; a normally closed fluid connection between said auxiliary pressure source and the piston of said by-pass valve; and means fluid coupled between said pressure supply means and said auxiliary pressure source and responsive to the failure of said pressure supply means for opening said normally closed fluid connection whereby said auxiliary pressure source actuates the piston of said valve, said piston moving said valve element to open said by-pass valve and permit free transfer of fluid between the ends of said cylinder.

5. A hydraulic control system comprising: a hydraulic cylinder; a piston positioned in said cylinder; first and second pressure sup-ply means; control means fluid connected between said first pressure supply means and opposite ends of said cylinder, said control means selectively applying pressure to opposite ends of said piston for moving said piston; a normally clos-ed by-pa-ss valve fluid coupled between opposite ends of said cylinder; piston means coupled to said by-pass valve for selectively opening said valve to uid connect the ends of said cylinder; a control valve, said valve comprising a housing having a chamber therein; a first fluid path communicating between o.ne end of said chamber and said first pressure supply means; a second fluid path communicating between the other end of said chamber and second pressure supply means; a third uid path communicating between said chamber at a point intermediate the ends thereof and said piston means; and a piston .positioned in the chamber of said control valve, said piston being maintained in a rst position Within said chamber by the differential pressure between the first and second supply means, said piston being responsive to the failure of said first pressure supply means for movement in said chamber to a second position, said piston, in both positions, iluid separating said first and second fluid paths, and fluid separating said first and third fluid paths, said second and third fluid paths being fluid separated by said piston in the first posi- Ytion thereof, and fluid coupled in the second position thereof whereby said second pressure supply actuates lsaid piston means to open said bypass valve and allow free movement of the piston within said cylinder.

6. In a hydraulic control system, the combination comprising a. hydraulic cylinder, a piston positioned within said cylinder for movement in either direction al-ong the axis of said cylinder, a source of fluid pressure, control means fluid coupled between said source and said piston for se- 'lectively applying the pressure from said source to opposite ends of said .piston to move said piston in either direction, a flui-d conduit coupled between Qpposite ends of said piston, a normally closed by-pass valve within said conduit, an auxiliary fluid pressure supply, fluid pressure responsive means coupled between said auxiliary supply and said by-pass valve for opening said bypass valve to permit fluid to flow freely through said conduit from one end of said piston to the other, and means fluid coupled between said fluid pressure responsive means and said auxiliary supply for applying pressure from said auxiliary supply to said fluid pressure responsive means to actuate said fluid pressure responsive means, the last-named means being fluid coupled between said source and said auxiliary supply and operable in response to failure of said source.

7. A hydraulic device for moving a movable member in either of two opposite directions, said device including differential pressure responsive means f-or moving the member in either direction, means fluid coupled to said differential pressure responsive means for selectively applying differential pressures to said responsive means to actua'te said responsive means, pressure responsive means fluid coupled to said differential pressure responsive means for equalizing the differential pressure across said diierential responsive means, the last-named pressure responsive means being normally inoperative, an auxiliary pressure supply, and control means fluid coupled between said auxiliary pressure supply and said Ilastnamed pressure responsive means for applying the pressure from said auxiliary pressure supply to said last-named pressure responsive means to operate said last-named pressure responsive means, said control means being operable upon failure of said differential pressure applying means.

8. A hydraulic device for moving a movable member in either of two opposite directions, said vdevice including differential pressure responsive means for moving the member in either direction, means fluid coupled to said differential pressure responsive means for selectively applying differential pressures to said differential pressure responsive means to actuate said differenti-al pressure responsive means, valve means fluid coupled to said differential pressure responsive means for equalizing the differential pressure across said differential pressure responsive means, said valve means being normally inoperative, an auxiliary pressure supply, and pressure responsive means fluid coupled between said auxiliary pressure supply and said differential pressure applying means for operating said valve means upon failure of said differential pressure applying means.

9. A hydraulic device for moving a movable member, said device including pressure responsive means for moving the member; means fluid coupled to said pressure responsive means for applying pressure to said pressure responsive mean-s to actuate `said pressure responsive means, norm-ally inoperative means ilui'd coupled to said .pressure responsive means for rendering said ypressure responsive mean-s ineffective to impede the movement of the movable member, an auxiliary pressure supply, and differential pres-sure responsive means uid coupled between said auxiliary pressure supply and the pressure applying means and responsive to a predetermined diiferential pressure between said pressure applying means and said auxiliary pre-ssure supply -to operate said normally inoperative means.

10. In combination: rst and second hydraulic devices, each of said devices comprising a cylinder, a movable piston positioned within said cylinder, pressure supply means fluid coupled to opposite ends of said cylinder for selectively applying pressure to opposite ends of said piston to move said piston, and a normally closed by-pass valve uid coupled between opposite ends of said cylinder; and differential pressure responsive means fluid coupled between the pressure supply means of said first and second hydraulic devices and operable upon failure of said pressure supply means of said first device for opening the bypass valve of said first device, said pressure responsive means being further operable upon failure of the pressure supply means of said second device for opening the by-pass valve of said second device, the opening of either of said by-pass valves permitting free movement of the piston of the hydraulic device associated with the open by-pass valve.

11. In combination: a first hydraulic system comprising a rst hydraulic cylinder, a rst pistn positioned within said cylinder, first pressure supply means, means fluid coupling said firstl supply means to opposite ends of said first cylinder for selectively applying pressure to the ends of said rst piston for moving said piston, and a normally closed first by-pass valve uid coupled between opposite ends of said rst cylinder; a second hydraulic system comprising a second hydraulic cylinder, a second piston positioned within said second cylinder, second pressure supply means, means uid coupling said second pressure supply means to opposite ends of said second cylinder for selectively applying pressure to the ends of said second piston for moving said piston, and a normally closed second by-pass valve fluid coupled between opposite ends of said second cylinder; rst control means coupled between said second supply means and said first by-pass valve for selectively opening said first by-pass valve to equalize the pressure at each end of said rst piston for permitting movement thereof second control means coupled between said first supply means and said second by-pass valve for selectively opening said second by-pass valve to equalize the pressure at each end of said second piston for permitting movement thereof; and means coupled between said first and second supply means and responsive to the failure of said first supply means for actuating said iirst control means, the last-named means being responsive to the failure of said second supply means for actuating said second control means.

12. A hydraulic control system for actuating a movable member, said system comprising: first and second hydraulic cylinders; first and second pistons positioned in said first and second cylinders, respectively, said rst and second pistons being connectable to the movable member; first and second uid pressure supply means; a rst control means for selectively applying pressure from said first pressure supply means to opposite ends of said first piston for moving said first piston; second control means for selectively applying pressure from said second pressure supply means to opposite ends of said second piston for moving said second piston, said rst and second control means being mechanically coupled for moving said first and second pistons simultaneously to jointly actuate the movable member; a normally closed by-pass valve fluid coupled between opposite ends of said rst cylinder; piston means coupled to said by-pass valve for selectively opening said valve and allowing a fluid connection between the ends of said first cylinder to permit free movement of said first piston; normally closed valve means fluid connected between said piston means and said second uid pressure supply means; and means coupled between said first and second pressure supply means and responsive to the failure of said first pressure supply means for opening said normally closed valve means whereby said second pressure supply means actuates said piston means to open said normally closed by-pass valve and permit free movement of said first piston within said rst cylinder.

DAVID GRANT. LELAND V. HALL.

REFERENCES CITED The following references are of record in the 

